perf(native): reduce Android screen-share latency

native-app/src/hooks/useHeliumStreamer.ts

@@ -32,6 +32,25 @@ interface UseHeliumStreamerResult {
   stopSharing: () => void;
 }
 
+async function applyLowLatencyEncoding(
+  sender: ReturnType<RTCPeerConnection["addTrack"]>,
+): Promise<void> {
+  const parameters = sender.getParameters();
+
+  if (!parameters.encodings || parameters.encodings.length === 0) {
+    return;
+  }
+
+  parameters.degradationPreference = "maintain-framerate";
+
+  const [firstEncoding] = parameters.encodings;
+  firstEncoding.maxBitrate = 1_200_000;
+  firstEncoding.maxFramerate = 24;
+  firstEncoding.scaleResolutionDownBy = 2;
+
+  await sender.setParameters(parameters);
+}
+
 function serializeIceCandidate(candidate: RTCIceCandidate): NativeIceCandidateInit {
   const raw = candidate as unknown as {
     candidate?: string;
@@ -125,7 +144,11 @@ export function useHeliumStreamer(
       setViewerCount(Object.keys(peersRef.current).length);
 
       localStream.getTracks().forEach((track) => {
-        peer.addTrack(track, localStream);
+        const sender = peer.addTrack(track, localStream);
+
+        if (track.kind === "video") {
+          void applyLowLatencyEncoding(sender);
+        }
       });
 
       peerWithHandlers.onicecandidate = (event): void => {

native-app/src/screens/StreamerScreen.tsx

@@ -8,7 +8,6 @@ import {
   Text,
   View,
 } from "react-native";
-import { RTCView } from "react-native-webrtc";
 
 import { useHeliumStreamer } from "../hooks/useHeliumStreamer";
 import { useAppTheme } from "../lib/theme";
@@ -30,7 +29,6 @@ export function StreamerScreen() {
     status,
     roomCode,
     viewerCount,
-    streamUrl,
     isSharing,
     startSharing,
     stopSharing,
@@ -150,16 +148,12 @@ export function StreamerScreen() {
         </View>
 
         <View style={styles.preview}>
-          {isSharing && streamUrl ? (
-            <RTCView
-              mirror={false}
-              objectFit="cover"
-              streamURL={streamUrl}
-              style={styles.video}
-              zOrder={0}
-            />
+          {isSharing ? (
+            <Text style={styles.previewPlaceholder}>
+              Screen capture active. Preview disabled to reduce latency.
+            </Text>
           ) : (
-            <Text style={styles.previewPlaceholder}>Screen preview appears after sharing starts</Text>
+            <Text style={styles.previewPlaceholder}>Start sharing to broadcast this phone screen</Text>
           )}
         </View>
 
@@ -278,10 +272,6 @@ function createStyles(theme: ReturnType<typeof useAppTheme>) {
       justifyContent: "center",
       overflow: "hidden",
     },
-    video: {
-      height: "100%",
-      width: "100%",
-    },
     previewPlaceholder: {
       color: theme.mutedForeground,
       paddingHorizontal: 16,